The instant invention relates generally to the propulsion of boats by means of sails, and more particularly concerns a detachable boat steering and sail propulsion unit suitable for application to a variety of small craft.
Conventionally, the sail arrangement or rig of a sailing boat and the hull design thereof are related to each other in a substantially permanent and unmodifiable fashion, and a sailboat has to be designed and built integrally as such. In other words, hull and propulsion means constitute a substantially inseparable whole, wherein the sail(s) side force is counteracted by the side resistance set up both by the underwater portion of the hull and one or more suitable appendages thereof -- e.g. fin keel(s), bilge keels, centerboard(s), leeboards, etc. -- which are so conceived as to prevent the boat from making excessive leeway, or sideward motion, under the action of a wind blowing from one side of the boat; a directional apparatus, or helm and rudder assembly, permits the boat to be steered.
In some traditional sailboats, which like the "topo" and "bragozzo" of the Venetian lagoon, or even the "sampan" from the China coasts, have been developed for operation in comparatively protected and shallow water or for sailing free (i.e. with the wind direction making an obtuse angle to the boat direction of travel), said side resistance comes partly from the shape of the hull bottom, featuring a sharp longitudinal corner or chine, and partly from a wide and shallow rudder configuration, the blade whereof has a greater area than usual. The latter configuration has the disadvantage that sailing on the wind (i.e. with the wind direction making an acute angle to the boat direction of travel) is virtually impossible and, moreover, owing to the strong side pressure acting on the rudder blade, steering in a breeze soon becomes a difficult and tiring job.
Known in the art are also some special outfits for converting small or collapsible structure boats, such as inflatable boats and folding canoes, for sail propulsion, wherein the sail(s), leeway-preventing means (typically, two leeboards), and rudder, complete with their respective attaching means, are provided as three separate assemblies for attachment to the boat own structure by their respective means at the moment of use. The effectiveness of such arrangements is generally good, but they tend to be bulky, costly and heavy, and quite often their erection requires considerable time due to their comparative complexity.